"As president of all Colombians, I categorically reject this attitude and make an impassioned plea for the end of hostilities," said President Juan Manuel Santos.

"What we are seeing are unacceptable acts that constitute criminal conduct and should be investigated by the authorities," Santos said Tuesday.

Santos visited the region last week, meeting with indigenous groups in the village of Toribio as members of the Revolutionary Armed Forces of Colombia flexed their muscle by setting up a checkpoint just outside the town. Santos was there to meet with villagers over their demands that both government soldiers and members of the FARC leave the area.

Santos was booed as he walked through the town.

He has seen his ratings among Colombians drop in recent weeks because of the widespread perception that the security situation has gotten out of control during his leadership.

A FARC commander of the Special Forces of the 6th Front told CNN last week that "Santos' war hasn't helped anyone here in this zone. He wants to increase the army and the police, which will not bring any benefit to the people or Toribio."

The commander said that if the government were to remove its soldiers from the zone, "FARC would have no reason to remain there," but promised the group would remain as long as the military is there.

"We've had enough deaths," said Feliciano Valencia, of the Cauca Indigenous Committee, in an interview with CNN en Español. "The humanitarian situation in the north of the department of Cauca is grave."

Given that neither the armed forces nor the FARC guerrillas have been able to solve the problem, "We have decided to play our cards in this matter," he said. "We want the armed actors to leave so that we can live in peace."